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Function File: 'N Must Be A Scalar Positive Integer'

This document contains code to define an Erlang B function and demonstrate its use. The erlangb function calculates blocking probability given traffic intensity and number of channels. The main file generates blocking probabilities for 1-4 channels over a range of traffic intensities and plots the results on a graph with legend and axis labels.

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M. H. Kabir
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66 views1 page

Function File: 'N Must Be A Scalar Positive Integer'

This document contains code to define an Erlang B function and demonstrate its use. The erlangb function calculates blocking probability given traffic intensity and number of channels. The main file generates blocking probabilities for 1-4 channels over a range of traffic intensities and plots the results on a graph with legend and axis labels.

Uploaded by

M. H. Kabir
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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Function File

% Define the erlang function


function B = erlangb(N, A)
if (length(N)~=1) | (fix(N) ~= N) | (N < 0)
error('N must be a scalar positive integer');
end
% TODO: test that elements of A are real and positive here?
esum = zeros(size(A));
for ii=0:N
esum = esum + A .^ ii ./ factorial(ii);
end
B = A .^ N ./ (factorial(N) .* esum);

Main File:
% ex1.m example for erlangb function
close all
clear all
lambda=0:0.0001:0.0065; % mean arrival rate (calls per second)
d=200; % mean duration (seconds per call)
a = lambda.*d; % traffic intensity in Erlangs
n = 1;
b = erlangb(n, a); % n channels/servers
ii=find(b<0.1);
plot(a(ii), b(ii), 'b')
hold on
n = 2;
b = erlangb(n, a); % n channels/servers
ii=find(b<0.1);
plot(a(ii), b(ii), 'g')
n = 3;
b = erlangb(n, a); % n channels/servers
plot(a, b, 'r')
n = 4;
b = erlangb(n, a); % n channels/servers
plot(a, b, 'k')
legend('1', '2', '3', '4 channels', 0)
xlabel('Traffic Intensity (Erlangs)');
ylabel('Blocking Probability');
title('Erlang B formula');
plot(a, 0.02, ':k') % 2% line

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